After several hours searching and trying things, I got my new Sony TV to work with JRiver playing HD video. My TV model is KDL-60W630B, bought last month, and I am using MC20. JRiver must be configured so the DLNA server video mode is 'Specified output format' If it is left at the default 'Specified output format only when necessary', then it fails no matter what format is specified (sometimes producing a few colored blocks, sometimes nothing at all). I left the output format at the default 'MPEG2/DVD NTSC stream'. None of the 'TS' formats work for me.
I also wanted to allow JRiver to negotiate the format to another player (my original Raspberry Pi xbmc for another HDMI TV works fine with JRIver default settings), so I followed the suggestion elsewhere in the Forum to add a new DLNA server for the Sony, and applied the above setting to this server only. The TV also has to be explicitly associated with this server.
I would prefer it if my new TV is able to play JRiver TV recordings in their native format (TS), because the above settings require fairly high CPU usage (50% of a Core i5 3 GHz). But I am happy I finally got it to work. Maybe Sony and/or JRiver will find the DLNA negotiating problem and a future update will fix this so others don't have this problem. Gizmo as a remote is fantastic.
--Bert